Snubbing means for semaphore signals



March 9, 1937.

SNUBBING MEANS FOR SEMAPHORE SIGNALS Filed June 21, I934 INVENTOR .5. C Bryan? sfc. BRYANT 4 2,073,575

Patented Mar. 9, 1937 SIG NALS

Stanley 0. Bryant, Des Plaines, Ill., assignor to General Railway Signal Company, Rochester,

Application June 21,1934, Serial No. 731,714

7 Claims. (01. 246-243) This invention relates to snubbing means for motor operated semaphore signals commonly used on railroads.

In the well known motor operated semaphore 5 signal, to which this invention relates, a series electric motor is directly connected by gearing to the semaphore signal; and when the semaphore drops/by its own weight to the caution or stop position, the armature of this motor is rotated backwardly. If a circuit is provided at this time around the motor, it will act as a generator to produce a dynamic braking or snubbing action to retard the downward movement of the semaphore and associated moving parts, thereby 15 avoiding objectionable shock and jar. It has been common practice to establish such a snubbing circuit by the automatic operation of circuit controlling means, which acts to close such circuit during the return movement of the sema- 20 phore, while maintaining the circuit open when the motor is being supplied with current to drive the semaphore to its raised position. Such a snubbing arrangement is disclosed, for example, in the patent to W. K. Howe, No. 1,092,266, April In accordance with the improvement constituting the present invention, rectifier or equivalent uni-directional current conducting device is connected across the armature and field of the 30 motor in series with a suitable resistance, the

rectifier being disposed to block the fiow of operating current and permit the flow of snubbing current generated when the motor is rotated backward during the return movement of the semaphore.

The invention contemplates the typical semaphore signal operating mechanism having the usual series motor, gearing, hold-clear devices and circuit controller; and since the particular 40 structure of such a mechanism is not material to the invention, and various types of such mechanism are well known in the art and in common use, it is not necessary to show or describe the structural detail of the mechanism.

5 The accompanying drawing illustrates in a simplified and diagrammatic manner one typical arrangement embodying the invention.

In this drawing the armature of the motor is designated A, the field F, and the hold-clear de- 50 vice I-IC, these being the usual and well-known parts of a semaphore signal operating mechanism. The usual circuit controller is illustrated in the drawing conventionally as comprising contact arms I and 2, assumed to move with the 55 semaphore blade through 90 degrees. Contact arm fl controls the operating circuits, and makes contactfwith fixed contact' members 3 and 4 'during the rnovement of the semaphore from its horizontal position nearly to the 45 degrees or caution condition, and from the caution position 5 nearly to the 90 degrees or clear position. The other contact arm 2 controls'the' circuits for the hold-clear device HO, and engages contacts 5 and 6 at the caution and clear positions.

The snubbing means of this invention is applied 10 to such a typical semaphore signal operating mechanism by providing a snubbing circuit permanently connected directly across or around the armature A and field F of the motor, this circuit including a resistance 1 and a suitable device R having uni-directional current conducting characteristics. This device R is preferably in the'form of a rectifier of the copper-oxide or other dry plate type. Any device ofiering substantially more resistance to the flow of direct current in one direction than in the other direction may be employed for the device R. It is not essential that the device R absolutely block the fiovv of current in one direction, so long as its resistance to the flow of current in that direction 5 or back leak, is relatively high as compared with the resistance of the armature and the field of the motor. Similarly, theresistance of the device R in conducting snubbing current may be relatively high, so long as it permits sufiicient current to flow to provide the desired dynamic braking or snubbing efiect at the voltage generated by the motor at a speed suitable for avoiding injurious shock and jars to the mechanism. For the ordinary type of semaphore signal operating mechanism in common use, a rectifier of the copper-oxide type, with an additional resistance 1, has been found to be well adapted for this use.

Semaphore signals may be controlled in various ways, not material to the present invention; and '40 in the typical arrangement illustrated, it is assumed that the signal G will be'controlled by a track relay T, and a line relay D, in accordance with common practice in automatic block signalling. The arrangement of circuits and mode of operation in this typical arrangement illustrated are familiar tothose skilled in the art; and a brief explanation will be sufllcient.

Assuming the semaphore is in its horizontal stop position, when the track relay T picks up, current is supplied from the battery B through the front contact 8 of said track relay, contacts I and 3 of the circuit controller, field F and armature A of the motor, back to the battery. The rectifier or equivalent device R is so disposed as to block the flow of this operating curent through the snubbing circuit. When the semaphore has been driven by the motor to its caution position, a circuit through the hold-clear device HC is established through the contacts 2-5 to hold the semaphore in this caution position if the line relay D is not energized. If, however, line relay D is energized, current is supplied through its front contact 9 and contacts I-4 to the motor to move the semaphore to its clear position, Where it is held by the hold-clear device HC supplied with current through contacts 2--6.

When the signal is controlled to assume its stop condition, as when the track relay T drops, the hold-clear device HC is de-energized and the supply of current to the motor is cut off, so that the semaphore may move down by its own weight, rotating the armature of the motor backward in so doing. As the armature of the motor is rotated, the residual magnetism in the field and armature cores initiates the generation of a voltage; and since the rotation of the armature is in the reverse direction to what it was when supplied with operating current, the generated voltage is in the opposite direction with respect to the operating voltage, with the result that current may flow through the device R and resistance 1. This flow of generated current induces a dynamic braking or snubbing which retards and regulates the downward movement of the semaphore to such a rate that it may be brought to rest in either the caution or stop position without objectional shock or jar. By selecting or adjusting the resistance 1 the rate of return movement of the semaphore may be regulated.

It will be noted that the snubbing action provided by this invention is effective throughout the return movement of the semaphore, and also does not require any contacts to open and close the snubbing circuit, with the difiiculties and disadvantages of adjustment, arcing, and the like.

Various adaptations and modifications may be made in the particular arrangement illustrated and described without departing from the invention.

What I claim is:

1. In a semaphore signal operating mechanism having a directly connected electric motor, a snubbing circuit comprising a uni-directional current conducting device connected across the field and armature of the motor, said device being arranged to prevent shunting of operating current around the motor and permit fiow of current generated by the reverse rotation of the armature during the return movement of the semaphore toward its stop position.

2. In a semaphore signal operating mechanism, the combination with a series electric motor, of a rectifier connected across the armature and field of the motor and arranged to conduct current generated by said motor during the backward rotation of the armature as the semaphore moves toward its stop position.

3. Means for snubbing semaphore signals operated by directly connected electric motors comprising, a circuit including a rectifier and resistance connected across the armature and field of the motor, said rectifier being arranged to block fiow of operating current which is supplied to the motor.

4. Semaphore signal operating mechanism comprising a series electric motor, a shunting circuit around said motor including a resistance, and a rectifier included in said circuit.

5. A snubbing device for motor operated semaphore signals comprising, a rectifier connected across the motor and arranged to block flow of op erating current which is supplied to the motor.

6. Means for snubbing and retarding the return movement of semaphore signals directly connected to electric motors comprising, a circuit of relatively low resistance permanently connected across the motor and including a rectifier poled to block motor operating current from flowing through said circuit.

7. In operating mechanism biased to move in one direction, a directly connected electric motor for moving the mechanism in the other direction, a snubbing circuit comprising a uni-directional current conducting device connected across the field and armature of the motor, said device being arranged to prevent shunting of operating current around the motor and permit flow of current generated by the reverse rotation of the armature during return movement of the mechanism in its biased direction.

STANLEY C. BRYANT. 

